Story highlights

Trump has received praise from various ultra-conservative European leaders

Like Trump, some European politicians have called for tightening the flow migrants

Washington (CNN)Donald Trump received more international criticism Tuesday, this time from London's newly elected mayor, Sadiq Khan.

The presumptive Republican presidential nominee had suggested Khan would be exempt from his proposed ban on Muslim foreigners entering the United States. But Khan, who is the first Muslim mayor of a major Western capital, wasn't impressed.

"Donald Trump's ignorant view of Islam could make both of our countries less safe -- it risks alienating mainstream Muslims around the world and plays into the hands of the extremists," Khan said.

Khan is not the only foreign political figure to slam Trump's controversial policies. British Prime Minister David Cameron, French Prime Minister Manuel Valls and German Chancellor Angela Merkel have been among those to take issue with the positions the billionaire businessman has laid out during his run at the White House.

But there is also a pocket of European politicians that has embraced Trump -- primarily on the far right of the political spectrum in countries including Italy, Belgium and France. Many of these politicians blame immigrants for the lack of jobs and a stagnant economy, have called for tighter borders and endorsed bans on refugees due to the growing threat of radical Islamic terrorism.

That's no accident, said James Thurber, director of American University's European Public Affairs and Advocacy Institute.

"They're probably doing it because (Trump) is very similar to their policies in respect to immigrants, with respect to nativism and nationalism within their own nations," Thurber said.

Trump launched his presidential bid by proposing to build a wall along the U.S.-Mexican border to stem the flow of undocumented immigrants into the United States. Later in his campaign, the billionaire businessman called for a temporary ban on Muslim immigrants to the United States.

Like the Republican candidate, some European politicians have called for tightening the flow migrants and refugees from Africa and the Middle East in the wake of terrorist attacks in Paris and Brussels.

Thurber said struggling economies also have contributed to the fear of immigrants -- and the popularity of Trump and his right-wing European fans -- particularly in the polarized political environments in both Europe and the United States.

"They're worried about immigrants coming in and taking their jobs, they're worried about social expenditures for the immigrants when they've got tight budgets," he said. "I think a lot of people in the United States are worried about their jobs also and threats by immigrants."

Across the European continent, here's a look at the praise some politicians are offering Trump.

Italy

Trump gained a notable foreign boost from one of Italy's leading right-wing politicians, Matteo Salvini. The head of Italy's Northern League party met Trump at a rally in Philadelphia the day before the businessman's sweeping win in the Pennsylvania primary in April.

The conservative Italian politician tweeted a picture of himself and the GOP front-runner and -- in Italian -- offered praise for the former reality TV star as well as criticism for President Barack Obama.

Asked about associating himself with the Italian dictator, Trump told NBC's Chuck Todd on "Meet the Press": "Look, Mussolini was Mussolini ... I know who said it. But what difference does it make whether it's Mussolini or somebody else? It's certainly a very interesting quote."